#include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x ostream& operator<<(ostream& os, const pair& p){ return os << "{" << p.first << ", " << p.second << "}"; } template ostream& operator<<(ostream& os, const vector& obj) { os << "{"; for (const auto& e : obj) os << e << ", "; return os << "}"; } template ostream& operator<<(ostream& os, const set& obj) { os << "set{"; for (const auto& e : obj) os << e << ", "; return os << "}"; } template ostream& operator<<(ostream& os, const map& obj) { os << "map{"; for (const auto& e : obj) os << e << ", "; return os << "}"; } #ifdef ONLINE_JUDGE #define dump(expr) ; #else #define dump(expr) { cerr << "\033[33m#L" << __LINE__ << ": " << expr << "\033[39m" << endl; } #endif struct E { int fr, to, c; E(int fr_, int to_, int c_) : fr(fr_), to(to_), c(c_) {} friend ostream &operator<<(ostream &os, const E &e) { os << "(" << e.fr << " -> " << e.to << ")"; return os; } }; typedef vector V; // typedef vector G; // note that each vertex will have both enterning edges & entered edges void add_edge(vector &vg, int fr, int to) { vg[fr].push_back(E(fr, to, 0)); vg[to].push_back(E(fr, to, 0)); } struct StronglyConnectedComponents { vector visited; vector t_order; vector comp; int n_comps; StronglyConnectedComponents() {} // normal topological sort void dfs1(vector &vg, int id, int &k) { visited[id] = true; for (auto it : vg[id]) if (it.fr == id && !visited[it.to]) dfs1(vg, it.to, k); t_order[--k] = id; } // dfs of reverse order void dfs2(vector &vg, int id, int &k) { visited[id] = true; for (auto it : vg[id]) if (it.to == id && !visited[it.fr]) dfs2(vg, it.fr, k); comp[id] = k; // foreach vertex "id", return the topological order } void exec(vector &vg) { int n = (int)vg.size(), k = n; // 1st dfs visited.assign(n, 0); t_order.assign(n, 0); comp.assign(n, 0); for (int j : range(n)) if (!visited[j]) dfs1(vg, j, k); // 2nd dfs visited.assign(n, 0); for (int i : range(n)) { int j = t_order[i]; if (!visited[j]) dfs2(vg, j, k), k++; } n_comps = k; } }; struct UF { vector data; UF(int n) : data(n, -1) {} int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); } bool find(int x, int y) { return root(x) == root(y); } void uni(int x, int y) { x = root(x); y = root(y); if (x != y) { if (data[x] < data[y]) swap(x, y); data[x] += data[y]; data[y] = x; } } }; ll solve() { int n, m; cin >> n >> m; vector as(m), bs(m), cs(m); for (int i : range(m)) cin >> as[i] >> bs[i] >> cs[i]; UF uf(n + 1); for (int i : range(m)) if (cs[i] == 1) { if (uf.find(as[i], bs[i])) return 1; uf.uni(as[i], bs[i]); } vector vg(n + 1); for (int i : range(m)) if (cs[i] == 2) { int a = uf.root(as[i]); int b = uf.root(bs[i]); if (a == b) return 1; add_edge(vg, a, b); } StronglyConnectedComponents scc; scc.exec(vg); map sizes; for (int i : range(n + 1)) sizes[scc.comp[i]]++; for (auto p : sizes) if (p.second > 1) return 1; return 0; } int main() { cout << fixed << setprecision(12); cout << (solve() ? "Yes" : "No") << endl; }